By implanting a specific element used as a dopant into a semiconductor crystal, a semiconductor having desired electrical properties can be manufactured. Inasmuch as the electrical properties of the semiconductor depend on a dose amount of the dopant, it is important to control the dose amount of the dopant implanted into the semiconductor. As a device for measuring a dose amount of a dopant, there is known, e.g., a Faraday cup.
Further, as examples of a technique for implanting a dopant into a semiconductor crystal, there are known an ion implantation technique and a plasma doping technique. In the plasma doping technique, ions or radicals included in plasma serve as a dopant which acts on a semiconductor crystal.
In case where the dose amount of the dopant is measured using the Faraday cup in the plasma doping technique, a tubular electrode used as a sensor is installed within a processing chamber. If plasma including a depositing gas is generated within the processing chamber, due to the ions or radicals included in the plasma, deposits adhere to the inside of the tubular electrode installed within the processing chamber. Adhesion of insulating deposits to the inside of the electrode reduces a measurement accuracy of the Faraday cup.
Further, in case where deposits adhere to the inside of the tubular electrode, it is difficult for a dry cleaning process to remove the deposits adhering to the inside of the electrode. As such, the electrode is taken out by opening a processing chamber and the deposits adhering to the inside of the electrode is removed by cleaning or other methods. This reduces a throughput when a doping process is performed with respect to a plurality of wafers.
Moreover, if the electrode of the Faraday cup is disposed within the processing chamber, it is sometimes the case that, when plasma is generated within the processing chamber, electric fields are concentrated on the electrode of the Faraday cup, eventually generating an abnormal discharge. If the abnormal discharge is generated, there may be a case where metal elements of the electrode are scattered within the processing chamber, consequently deteriorating characteristics of a device subjected to a doping process.
In addition, while charged particles can be measured using the Faraday cup, it is impossible for the Faraday cup to measure electrically neutral particles such as radicals or the like. For that reason, it is difficult for the Faraday cup to measure a dose amount of a dopant including radicals in the plasma doping technique.